Digital microfluidics has been emerging as a promising development in lab-on-a-chip (LoC) systems [1-5]. A variety of droplet actuation methods have been conducted, including thermal Marangoni effect [6], photosensitive surface treatment [7], surface acoustic wave [8], liquid dielectrophoresis [9] and electrowetting [10, 16-19]. Among these techniques, electrowetting draws attention due to its high performance, reliability, simplicity and fast response. Based on the droplet manipulation, one is able to integrate different cumbersome laboratory operations in a microliter liquid, called lab-in-a-drop [11]. Increasing numbers of assays have benefited from this innovation, such as polymerase chain reaction (PCR) [12] and cell sorting [13]. Lately, addressable electrowetting has been exploited to extend the technique [14]. An optoelectrowetting (OEW) approach proposed by Chiou et al. employs a photoconductor, making “virtual electrodes” [15]. The electrodes are generated dynamically with projected images, realizing multi-droplet and programmable manipulations. A voltage is applied across two parallel plates, one above and one below a droplet in a closed configuration which seriously inhibits integrating additional components or extensibility.